Analytische Chemie
Filtern
Dokumenttyp
Sprache
- Englisch (2)
Referierte Publikation
- nein (2) (entfernen)
Schlagworte
- In situ measurement (2) (entfernen)
Organisationseinheit der BAM
In situ chemical analysis of duplex stainless steel weld by laser induced breakdown spectroscopy
(2024)
The high corrosion resistance and good mechanical properties of duplex stainless steel (DSS) are due to its special chemical composition, which is a balanced phase ratio of ferrite (α) and austenite (γ). Many industrial applications require the integration of DSS components. For this, Gas tungsten arc welding (GTAW) is an excellent choice, as it allows an automated operation with high reproducibility. However, when the weld pool solidifies, critical ratios of α- and γ- phases can occur, which lead to solidification cracking, increased susceptibility to corrosion, and a decrease in ductility and critical strength. Previous studies have shown that these defects can be caused by the accumulation of manganese and chromium in the heat affected zone (HAZ), requiring ongoing monitoring of this accumulation. A suitable method for such monitoring is laser-induced breakdown spectroscopy (LIBS), which can be used in two operating modes: calibration using standard reference samples and calibration-free. Unlike conventional quantitative LIBS measurements, which require reference samples to generate a calibration curve, calibration-free LIBS (CF-LIBS) allows chemical compositions to be determined solely from the emission spectrum of the plasma. Numerous publications show that CF-LIBS is a fast and efficient analytical method for the quantitative analysis of metal samples. In this work, CF-LIBS is applied to spectra obtained during GTAW DSS welding and the result is compared with those obtained by PLS analysis. A good correlation was found between both types of analysis, demonstrating the suitability of the CF-LIBS method for this application. The CF-LIBS method has a significant advantage over conventional LIBS due to the rapid in situ measurement of concentrations of major alloying elements without calibration procedure. This, combined with fast feedback and appropriate adjustment of welding parameters, helps prevent welding defects.
A laser induced breakdown spectroscopy (LIBS) system was combined with the Gas Tungsten Arc (GTA) Welding process for the in situ measurement of chemical compositions in austenitic stainless steels during welding. The purpose of this project is to develop a prototype of an online chemical composition control system for welding applications. One of the use cases of this new LIBS-based measurement system can be the controlling of potentially dangerous emissions during the welding process in order to improve the working safety conditions. Further, the control of the weld pool composition allows governing the weld pool solidification behavior and thus allows reducing the resultant susceptibility for solidification cracking. The composition of the weld seam is from the metallurgical point of view the most critical parameter for the occurrence of weld defects1. Conventional inspection methods for weld seams as e.g. ultrasonic inspection are ex situ and cannot prevent the defects. For that reason automated in situ analysis systems for weld defect detection are much more efficient2. Beyond that, the proposed LIBS-based analysis system allows to study the correlation between the occurrence of weld defects and the chemical composition of the weld pool or the region where solid and liquid phase coexist.